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First Aid and Emergencies

Insect and Spider Bites and Stings

Prevention - Home Treatment - When to Call a Health Professional

Insect and spider bites and bee, yellow jacket, and wasp stings usually cause a localized reaction with pain, swelling, redness, and itching. In some people, especially children, the redness and swelling may be worse, and the local reaction may last up to a few days. In most cases, bites and stings do not cause reactions all over the body. (In a few areas, mosquitoes may spread illnesses, including encephalitis and malaria.)

Some people have severe skin reactions to insect or spider bites or stings, and a few have allergic (anaphylactic) reactions that affect the whole body. Symptoms may include hives all over the body; shortness of breath and tightness in the chest; dizziness; wheezing; or swelling of the tongue and face. If these symptoms develop, immediate medical attention is needed.

Spider bites are rarely serious, although any bite may be serious if it causes a person to have an allergic reaction.

Black widow spiders can be up to 5 cm (2 inches) across (although they are generally much smaller) and are shiny black with a red hourglass mark on their undersides. Their bites may cause chills, fever, nausea, and abdominal muscle pain. A person having a severe reaction may have difficulty breathing. People with high blood pressure, elderly people, and children have the greatest risk of having a severe reaction.

Brown recluse (fiddler) spiders are smaller than black widows and have long legs. They are brown with a violin-shaped mark on their heads. Their bites result in intense pain (although the bite itself may be painless) and a blister may develop that turns into a large, open sore. Their bites also may cause nausea, vomiting, headaches, and chills.

Also see Tick Bites on See Tick Bites.


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  • To avoid bee stings, wear white or light-coloured, solid fabrics. Bees are attracted to dark colours and flowered prints.

  • Avoid wearing perfumes and colognes when you are outside.

  • Apply an insect repellent containing DEET every few hours when in insect- and spider-infested areas. Use a lower-concentration DEET product for small children and pregnant women. Wash DEET off when you come inside. Alpha Keri and Skin-So-Soft bath oils also seem to repel insects.

  • Wear gloves and tuck pants into socks when working in woodpiles, sheds, and basements where spiders are found.

Home Treatment

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  • Remove a bee stinger by scraping or flicking it out (if the stinger isn't visible, assume there isn't one). Don't squeeze the stinger; you may release more venom into the skin.

  • If the bite is from a black widow or brown recluse spider, apply ice to the bite and call your doctor.

  • Apply a cold pack or ice cube to the bite or sting. Some people also find that applying a paste of baking soda, meat tenderizer, or activated charcoal mixed with a little water helps relieve pain and decrease the reaction.

  • Take an oral antihistamine (such as Benadryl or Chlor-Tripolon) to relieve pain, swelling, and itching if there are many bites. Calamine lotion or hydrocortisone cream may also help.

  • Carry an emergency kit containing a syringe and adrenaline (epinephrine) if you have had a severe allergic reaction to insect venom in the past. Ask your doctor or pharmacist how to use the kit.

  • Trim your fingernails to prevent scratching, because scratching can lead to infection.

When to Call a Health Professional

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Call 911 or seek emergency services if signs of a severe allergic reaction develop soon after you have been bitten or stung by an insect or spider:

  • Wheezing or difficulty breathing.

  • Swelling around the lips, tongue, or face, or significant swelling around the site of the bite or sting (e.g., entire arm or leg is swollen).

  • Spreading skin rash, itching, feeling of warmth, or hives.

Call your doctor:

  • If you have been bitten by the same type of spider or insect that previously caused a serious reaction.

  • If a blister appears at the site of a spider bite, or if the surrounding skin becomes discoloured.

  • If symptoms are not improving in 2 to 3 days or if signs of infection develop:

    • Increased pain, swelling, redness, or tenderness.

    • Heat or red streaks extending from the area.

    • Discharge of pus.

    • Fever of 37.8°C (100°F) or higher with no other cause.

  • To talk about adrenaline kits or allergy shots (immunotherapy) for insect venom if you have had a serious allergic reaction.

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